1. Field of the Invention
The present invention relates to the transmission and reception of data originating from, and received by, data transmission machines.
2. Background of the Invention
FIG. 1 illustrates a first prior art point-to-point delivery system for digitally encoded message (DEM) data. In such a system, a message communicating device (MCD) 1 can deliver DEM data to another MCD 5. MCD 1 first enables connection 10 between MCD 1 and a public-switched telephone network (PSTN) 3. PSTN 3 then enables connection 30 between PSTN 3 and MCD 5, creating a point-to-point connection between MCD 1 and MCD 5, through PSTN 3. In the opposite direction, MCD 5 transmits DEM data to MCD 1 by activating connections 70 and 90.
The arrows in FIGS. 1-4 and in FIG. 6 point in the direction of the initial contact from the initiator of a connection to the respondent.
FIG. 2 illustrates a second prior art system, which uses an intermediate enhanced service message handler (ESMH) 4. This system requires two point-to-point connections instead of the single point-to-point connection required for the first prior art system. ESMH 4 can provide send-side service (store-and-forward functionality), receive-side service (mailbox functionality), or both, to its customer, the user of MCD 1. To send DEM data to MCD 5, MCD 1 first activates connection 10, connecting MCD 1 to PSTN 3. PSTN 3 then activates connection 41 to ESMH 4. The DEM data is then transferred from MCD 1 to ESMH 4, and stored. Connections 10 and 41 can then be broken off. ESMH 4 then forwards the DEM data through PSTN 3 to MCD 5, using connections 51 and 31.
When MCD 5 sends DEM data to MCD 1, ESMH 4 provides receive-side service for its customer, the user of MCD 1. MCD 5 transmits the DEM data to ESMH 4 through connections 70 and 42. ESMH 4 then stores the DEM data, until the data is picked up by MCD 1. MCD 1 initiates pickup through connection 13 to PSTN 3, and through connection 43 between PSTN 3 and ESMH 4. Once pickup is initiated, a copy of the DEM data is transmitted from ESMH 4 to MCD 1, using connections 43 and 13. U.S. Pat. No. 4,922,348 discloses a similar ESMH facsimile transmission system.
The send-side functionality of the apparatus illustrated in FIG. 2 forces the customer to choose between (1) always sending DEM data to the ESMH 4 for re-transmission, and (2) having to make a choice between using a direct point-to-point delivery, as illustrated in FIG. 1, and using ESMH 4. Option (1) imposes unnecessary costs when a point-to-point delivery is available. Option (2) requires the customer to make a specific decision each time the system is used. For example, the customer may decide to use ESMH 4 because she has good reason to believe that a direct connection will fail, or because she needs to use a "value-added" feature of ESMH 4, such as deferred delivery. Moreover, the way that MCD 1 is used will differ depending upon whether the customer chooses point-to-point delivery or delivery through ESMH 4. This is a disadvantage to the customer, who has to learn two procedures, and know which one to use for each particular circumstance.
The receive-side functionality of the system illustrated in FIG. 2 also results in costs and delays. The customer cannot determine when DEM data is available for pickup without periodically calling back to ESMH 4 through MCD 1. These calls represent an unnecessary cost when there is no DEM data queued for pickup. Furthermore, unless ESMH 4 is monitored continually, there is an inevitable delay between the time the data is ready to be picked up, and the time it is actually picked up.
FIG. 3 illustrates a third prior art system, which is specific to facsimile store-and-forward networks. The third prior art system uses a network access device (NAD) 7 to improve the system illustrated in FIG. 2. NAD 7 makes routing decisions on behalf of the end-user of the facsimile communicating device (FCD) 6, using an address-based algorithm. After the user inputs the destination address at the user interface for FCD 6, NAD 7 decides either to attempt point-to-point delivery via connections 21 and 30, or to re-route the transmission through facsimile store-and forward switch (FSFS) 8, using connections 21 and 41. In the latter case, FSFS 8 performs normal store-and-forward processing as described above in connection with ESMH 4 in FIG. 2, and makes final delivery to FCD 9 through connections 51 and 31. U.S. Pat. No. 5,014,300 discloses a facsimile store and forward network based upon a network access device.
However, the use of an address-based algorithm for routing determination assumes that the end-user's routing decisions are based entirely on the cost of the transmission. The algorithm is designed to implement delivery through FSFS 8 whenever a transmission cost advantage is identified. For example, the algorithm may simply distinguish a local from a long-distance address, and route through FSFS 8 when it encounters the latter. This type of cost-based routing is becoming obsolete due to the considerable drop in the cost of long-distance direct dialing.
The more efficient use of telephone lines, discussed below, has become the more salient factor in send-side routing decision making. As a result of this shift, demand for ESMH systems, e.g., electronic mail and electronic data interchange (EDI), that avoid long distance charges by offering local point-of-presence dial-up for users, has not met expectations. Other ESMH systems that historically attempted direct, point-to-point connection first, e.g., voice mail and enhanced fax services, are experiencing slow growth.
FIG. 4 illustrates a fourth prior art system which improves receive-side, mailbox functionality by using a receive access device (RAD) 7a. RAD 7a is equipped with a radio-frequency (RF) receiver, to facilitate notification of delivery and automatic retrieval for DEM data received by the ESMH. MCD 5 establishes a send path to ESMH 4a through connection 70, PSTN 3, and connection 42. MCD 5 then transmits the DEM data to ESMH 4a, and severs the connection. ESMH 4a initiates RF transmission processing along path 83, to notify RAD 7a that DEM data is available for pickup. RAD 7a responds by creating connection 24 to PSTN 3, completing the path through connection 44 to ESMH 4a. As ESMH 4a queues the relevant DEM data for transmission, RAD 7a rings back to MCD 6a to provide a point-to-point connection between ESMH 4a and MCD 6a. ESMH 4a then transmits the DEM data sent by MCD 5 to MCD 6a over connections 44, 24, and 94. U.S. Pat. Nos. 4,942,599 and 4,969,184 disclose RF notification systems similar to the system illustrated in FIG. 4.
This type of RF notification system is limited to MCD users within, typically, a 50-mile radius of an RF transmitter. Within the covered area, signaling difficulties are common. In city areas, for example, tall buildings create "caverns" that hinder the reliable delivery of RF signals. Furthermore, because the commercial costs of two-way RF-based transmission are prohibitive, it is possible only to send notification, and impossible to verify its receipt. Even the cost of one-way RF-based notification might prove prohibitive. Finally, the system illustrated in FIG. 4 cannot handle all formats of DEM data transmissions. It is limited to DEM data transmission formats using send and receive protocols that allow either a "sender" or a "receiver" of data to, interchangeably, assume an initiating role. For example, note that RAD 7a had to initiate a calling sequence, or protocol, to both MCD 6a and ESMH 4a in order to create an end-to-end connection between them. Both MCD 6a and ESMH 4a responded to RAD 7a by assuming receive postures. In this situation, unless the data transfer protocols for the particular format of DEM data waiting to be delivered are set up to allow a "receiver" to initiate data transmission, ESMH 4a will never be prompted to send data to MCD 6a. For similar reasons, the system illustrated in FIG. 3 would be incapable of handling formats of DEM data other than the specific formats and associated protocols for which it was designed.
For send-side functionality, phone-line availability is replacing cost as the critical consideration for routing of DEM data. The percentage of busy signals and no-answer situations encountered by MCDs has increased considerably over the last few years. The incidence of non-completed calls for facsimile communications is particularly high, and is estimated to be four to five times that of normal, voice-based communications. The diminishing importance of cost of delivery is associated with an increasing user preference for routing sequences that attempt point-to-point transmission as a first option. A backup store-and-forward function should be available as a second option without requiring the user to re-enter the addressing information.
Similarly, for receive-side functionality, users want their local PSTN to attempt a direct connection to their phone line first. If the phone line is unavailable, a backup mailbox should initiate an automated procedure to transmit the intercepted DEM data to the receiving MCD as soon as a phone line becomes available.
Typical users in a business environment want their MCD(s) and phone line(s) to be in use whenever they are available. Typical users in home-centered work environments must increasingly rely on DEM data storage and routing solutions. Such users only have one or two telephone lines available. Because those lines are often used for other communications, they are often not available for direct point-to-point delivery of DEM data.